The present embodiments relate to reducing the widening of a radiation beam in a medical radiation therapy system.
Radiation therapy includes a medical therapeutic method for the treatment of tumor diseases. High-energy photon radiation (e.g., x-ray radiation, gamma radiation) or particle radiation (e.g., electrons, protons, ions) is directed toward an area of the patient's body that is to be treated. However, radiation therapy may be used in non-therapeutic fields, for example when irradiating phantoms or non-living objects in the context of research, or when irradiating materials.
Particle beam therapy includes generating high-energy particle radiation with an acceleration device. The particles accelerated to high energy are formed into a particle beam and subsequently directed toward the tissue to be irradiated. The particles penetrate the tissue to be irradiated and then dissipate their energy into a localized area. The depth of penetration of the particle beam into the tissue to be irradiated is primarily a function of the particle beam's energy. The higher the particle beam's energy, the deeper the particles penetrate into the tissue to be irradiated. In comparison with conventional irradiation methods that work with x-ray and electron beams, particle beam therapy is characterized in that the energy of the particles is dissipated in a localized and distinguishable area. Consequently, in comparison with conventional irradiation methods, a tumor, for example, can be irradiated more precisely, and surrounding tissue can be preserved better.
Particle beam therapy is generally performed in a special particle beam therapy system. In one area of the system, the particle beam is generated and transported to several rooms. In another area, different rooms exist, in which patients are prepared for an upcoming irradiation session or irradiated during an irradiation session.
FIG. 1 shows a schematic overview of a configuration of a particle beam therapy system 1 according to the subsequent publication DE 10 2008 005 068 A1. Ions such as, for example, protons, pions, helium ions or carbon ions are principally used as particles. Particles may be generated in a particle source 2. If, as shown in FIG. 1, two particle sources 2 generate two different types of ions, it is possible to switch between the two types of ions within a short time interval. A switching magnet 3, for example, is used to switch between the two types of ions. The switching magnet 3 is disposed between the ion sources 2 and a pre-accelerator 4. The particle beam therapy system 1 can be operated with protons and with carbon ions simultaneously.
The ions generated by the ion source or one of the ion sources 2 and where applicable selected by the switching magnet 3 are accelerated to a first energy level in the pre-accelerator 4. The pre-accelerator 4 is, for example, a linear accelerator. The particles are then fed into an accelerator 5, for example, a synchrotron or cyclotron. In the accelerator 5, they are accelerated to high energies, such as are required for irradiation. After the particles have exited the accelerator 5, a high-energy beam transport system 6 guides the particle beam to one or more irradiation rooms 7. In an irradiation room 7, the accelerated particles are directed onto a body part that is to be irradiated. The accelerated particles are directed onto the body part from a fixed direction or else from different directions by a rotatable gantry 9 that is movable about an axis 8.
The particle beam therapy system 1 has different rooms 10 in which for example patients are prepared for an upcoming irradiation session or an upcoming examination. These further rooms 10 and the irradiation rooms 7 are connected to one another by corridors.
FIG. 2 shows a schematic overview of the “inner workings” of a proton irradiation system according to EP 0 864 337 A2. After generation and acceleration of a proton beam 21, the cross-sectional dimensions of the proton beam 21 are adjusted by magnet systems 22. A switching unit 23 ensures that the proton beam 21 can be switched off at any time. The proton beam 21 reaches a radiation head 20 or “nozzle”. The radiation head 20 includes two deflecting magnets 24, a quadruple magnet 25 that focuses the proton beam 21, an adjusting system 26 that adjusts the energy of the particle beam 21, a collimator lens unit 27 for adjusting the beam form, and a detector system 28 for monitoring the radiation dose dissipated. The proton beam 21 then leaves the radiation head 20 and strikes a patient 30 who is immobilized on a treatment table 29.
When planning medical irradiations, the air gap crossed between beam output and patient is considered, since this gap can cause the widening of a radiation beam as a consequence of multiple scattering.